This invention relates generally to surgical tools and particularly to powered microsurgical tools of novel construction.
Surgical cutting tools, such as scalpels and saws are well known in the art. Many manual tools have been miniaturized to enable a surgeon to perform minute incisions, often in closely confined areas. A major difficulty with all such tools is that the surgeon must supply the required cutting force by means of a sawing or slicing motion. At best, such miniature tools are restricted to exposed areas of the body to which the surgeon has access or to areas which have been exposed by major surgery.
The novel surgical cutting tool of the invention is powered by a remote drive means and removes the requirement for the surgeon to provide the cutting force. All the surgeon need do is guide the tool. The tool in its fundamental form consists of a rotatable work wheel, i.e. a cutting blade that is mounted at the end of a casing member which in one embodiment includes a rigid tubular section that enables the surgeon to handle it as a conventional scalpel. The tool is also readily adapted to receive a grinding head for abrasive use. In another important version of the invention, the tool is positioned at the end of a miniature flexible catheter for enabling intravascular use, i.e. within the walls of blood vessels such as arteries.
In intravascular surgery, and especially in coronary atherectomies, a catheter coupled device should not endanger the walls of the artery and must be readily flexed around bends while still performing smoothly. Ideally, the tool should be capable of slicing through frontal obstructions or occlusions, not produce loose materials or fragments, and move through the artery with minimal resistance, often while being fed over a guide wire.
The flexibility of the drive system of the invention permits the surgeon to freely manipulate a small slender hand-held tool with relative ease within the proximity of his operating area. The microsurgical tool of the invention is a powerful machine that only requires the surgeon to provide guidance for the tool. In difficult access areas a conventional scalpel often must be held near the end of the handle farthest from the blade. In such a position, every movement of the surgeon's hand is amplified by the length of the scalpel and applying a controlled cutting force is very difficult. With the invention, the powered work wheel (cutting blade) does the work. The cutting blade can be selected to provide a safe, limited depth of cut and eliminate the need for multiple shallow cuts to achieve a desired cut depth as is required with conventional manual scalpels. With the invention, a single clean cut is achieved.
The circular work wheel (blade or abrasive head) of the invention is coupled to a drive hub that rotates about an axis at the distal end of a casing member, which in the preferred embodiments, is a tube or catheter. The surface of the drive hub is treated to improve the grip of a plastic monofilament drive line that extends through the catheter and loops around the drive hub. In the preferred embodiments, the drive hub surface is formed with sharp edges that superficially bite into the monofilament. Also, tensioning is applied to the drive line near the drive hub and the casing member is a multiple or multi lumen device with the pulling (take up) portion and the feeding (payout) portion of the drive line being in separate lumens and maintained out of contact with each other for minimum resistance.